ABSTRACT The goals of the human mast cell and tissue acquisition Core B are focused and straightforward: to provide key services that will be used by all three Projects. Core B will provide well-defined materials to each of these projects to ensure coordinated methods of approach, and will be available to troubleshoot if problems arise. Located at the Northwestern University Feinberg School of Medicine under the leadership and supervision of Dr. Bruce Bochner, Core B will procure, catalog, store and ship de-identified biopsy samples from subjects with chronic rhinosinusitis, eosinophilic gastrointestinal disorders and atopic dermatitis in collaboration with physicians and scientists located at Northwestern for use primarily by Project 3. A second important task for Core B is to generate enriched mature human mast cells derived from tissues such as discarded human skin, as well as samples of human large intestine and lung resection specimens from the Northwestern Memorial Hospital for use in in vitro experiments. The third focus of Core B is to assist with and directly generate ?humanized? mast cell mice employing a method by which CD34+ human cells are transplanted into the triple transgenic NSG-SGM3 (NSGS) mice expressing human IL-3, GM-CSF and SCF. Finally, the fourth responsibility of Core B is to maintain important human and mouse mast cell lines, and to generate culture- derived mouse mast cells from bone marrow of mice expressing human Siglecs and from the bone marrow of the transplanted NSGS mice to generate culture-derived human mast cells, the latter two for use primarily by Projects 1 and 2. In short, Core B will provide an efficient, standardized and centralized source for mast cells, humanized mast cell mice, and human tissue specimens. The experience and expertise in isolating and generating mast cells will be critical to the success of Project 1 and Project 2, while the availability of de- identified biopsies and discarded surgical tissues from well-characterized cohorts of patients and controls are essential to the aims of Project 3.